Cultures containing cellular matter may be employed to study pathogenic material such as bacteria and viruses. For example, pathogen-impermeable containers having an interior surface coated with a layer of solid or semisolid medium within which cells are grown may be inoculated with the desired type of cells. After the cells are subjected to conditions appropriate for cultivation, they may be removed from the containers as a suspension and may optionally be concentrated. Also, if desired, viral matter may be extracted from the cells after removal from the containers.
Pathogenic substances, however, including viruses (such as the human immunodeficiency virus (HIV), rabies, and herpes) and bacteria (such as bacillus anthracis, yersinia pestis, and those of the streptococcus genus), must be handled with extreme care to prevent release of the pathogen. In addition, there exists a need in pharmaceutical, biotechnological, and other scientific industries to quickly screen, identify, and/or process large numbers or varieties of fluids, pathogenic or otherwise. As a result, much attention has been focused on developing efficient, precise, and accurate fluid handling methods that may be used, for example, to carry out screening assays and/or combinatorial techniques. Since fluids used in pharmaceutical, biotechnological, and other scientific industries may be rare and/or expensive, techniques capable of handling small volumes of fluids provide readily apparent advantages over those requiring relatively larger volumes. Furthermore, as pathogenic fluids represent a potential safety hazard, it is also desirable to reduce the quantities used to carry out studies or investigations involving such substances.
Typically, fluids for use in combinatorial methods are provided as a collection or library of organic and/or biological compounds. In many instances, such libraries and collections are provided in a well plate format for screening and/or processing. Well plates are typically single-piece in construction and comprise a plurality of identical wells, wherein each well is adapted to contain a small volume of fluid. Such well plates are commercially available in standardized formats and sizes, and may contain, for example, 96, 384, 1536, or 3456 wells per well plate. Fluids are typically transferred from such well plates, e.g., during formatting and reformatting procedures, using devices that require contact between the fluid to be transferred and a solid surface of a device. For example, capillaries (Eppendorf-type or otherwise) having small interior channels are commonly employed for sample fluid handling by submerging their ends into a pool of sample. Pipetting systems, whether automated, robotic, or otherwise, that have submergible tips may be employed as well. Contact between the solid surface and the fluid to be transferred typically results in surface wetting that represents a source of unavoidable fluid waste as well as a source of potential pathogenic contamination. In addition, if more than one fluid is to contact an interior or exterior solid surface of a non-disposable capillary or pipette tip, the surface must be washed between sample transfers in order to eliminate cross contamination and sample carry-over. The liquid biohazard waste created from this wash process must then be disposed of and rendered harmless. It would be desirable to avoid liquid waste generation from repeated wash processes and eliminate additional storage and disposal costs. Disposable pipette tips or capillaries may be used to avoid the generation of liquid waste. However, disposal of solid waste also incurs storage and disposal costs.
Thus, there is a need for fluid handling systems that enable safe and convenient handling, formatting, and reformatting of potentially dangerous bacterial, viral, and other pathogenic specimens. Such fluid handling systems may be used, for example, to perform clinical diagnostic tests, engage in high-throughput drug screening, and carry out growth inhibition studies. In order to ensure that pathogens are not released during fluid handling procedures, pathogen-impermeable enclosures such as glove boxes may be used to contain the pathogenic specimens. Small volume pathogenic cultures, however, often require complicated manual manipulations, which are not easily carried out using glove boxes; thus, performing such procedures in a glove box would likely introduce error during handling and result in possible unwarranted experimental conclusions. Various automated devices to control fluid transfer in closed systems for culturing living pathogens have been developed. U.S. Pat. No. 6,022,742 to Kopf, for example, describes one such automated device.
The use of acoustic energy in printing technology is also known. For example, U.S. Pat. No. 4,308,547 to Lovelady et al. describes a liquid drop emitter that utilizes acoustic principles to eject liquid from a body of liquid onto a moving document in order to form characters or barcodes thereon. Lovelady et al. is directed to a nozzleless inkjet printing apparatus, wherein controlled drops of ink are propelled by an acoustical force produced by a curved transducer at or below the surface of the ink. In contrast to capillaries, syringes, pipettes, inkjet print heads, and other such fluid dispensing devices that employ a nozzle, tip, or tubing for fluid transfer, nozzleless fluid ejection devices as described in the aforementioned patent do not contain components requiring cleaning and/or disposal after use. In addition, disadvantages associated with nozzles or tips in fluid dispensing systems, including clogging, misdirected fluid, improperly sized droplet formation, and the like, are avoided. More recently, acoustic ejection has been employed in contexts other than in ink printing applications. For example, U.S. Patent Application Publication No. 20020037579 to Ellson et al. describes the use of focused acoustic radiation to dispense fluids with sufficient accuracy and precision to prepare biomolecular arrays from a plurality of reservoirs.
Acoustic radiation has also been used to assess the contents of a container adapted to contain a liquid. Traditionally, the contents may be assessed by contacting a sensor with the liquid (see U.S. Pat. No. 5,507,178 to Dam), or by transmitting acoustic radiation through an open top of a container and detecting radiation reflected from an air-liquid interface of the container back to the sensor (see U.S. Pat. No. 5,880,364 to Dam). More recently, U.S. patent application Ser. No. 10/010,972, Publication No. 20030101819, “Acoustic Assessment of Fluids in a Plurality of Reservoirs,” inventors Mutz, Ellson, and Foote, filed on Dec. 4, 2001, describes an improved acoustic assessment technique that involves the transmission of acoustic radiation through a reservoir to assess the fluid contents within the reservoir without requiring direct contact with the fluid contents therein. By analyzing a characteristic of the acoustic radiation transmitted through the fluid, various properties of the fluid within the reservoir may be determined. This type of acoustic monitoring may be used advantageously in conjunction with optically opaque reservoirs.
Similarly, focused acoustic energy recently has been used in applications involving biological matter such as living cells. For example, a number of U.S. patent applications describe the use of focused acoustic radiation to manipulate and sort cells. See U.S. Patent Application Publication No. 20020064808 to Mutz et al.; U.S. patent application Ser. No. 09/999,166, Publication No. 20020142286, filed Nov. 29, 2001, for “Focused Acoustic Energy for Ejection Cells from a Fluid,” inventors Mutz and Ellson, assigned to Picoliter, Inc. (Mountain View, Calif.); U.S. Patent Application Publication No. 20020064809 to Mutz et al.; and U.S. patent application Ser. No. 10/040,926, Publication No. 20020090720, filed Dec. 28, 2001, for “Focused Acoustic Ejection Cell Sorting System and Method,” inventors Mutz, Ellson, and Lee, assigned to Picoliter, Inc. (Mountain View Calif.). Furthermore, the use of focused acoustic radiation has been described for preparing and analyzing a cellular sample surface. (See U.S. patent application Ser. No. 10/087,372, Publication No. 20020171037, filed Mar. 1, 2002, entitled “Method and System Using Acoustic Ejection for Preparing and Analyzing a Cellular Sample Surface,” inventors Ellson, Mutz, and Caprioli.)
The use of focused acoustic energy in the context of applications involving pathogenic fluids, however, has previously been unknown in the art. Thus, through the use of focused acoustic radiation, the invention provides previously unrealized opportunities in pathogenic studies.